Constant speed pump and motor hydraulic transmission



Oct. 7, 1952 .1. E. BEvlNs 2,612'753 CONSTANT SPEED PUMP AND MOTORHYDRAULIC TRANSMISSION Filed Nov. fr, 1947 s sheets-sheet 1 INVENTOR nATTO R N EY Oct. 7, 1952 J. E. BEvlNs 2,612,753

CONSTANT SPEED PUMP AND MOTOR HYDRAULIC TRANSMISSION Filed Nov. 7, 19475 Sheets-Sheet 2 INVENTOR '2 ml/E5 E. BEV/N5 BY M 1/ M ATTORNEY Oct. 7,1952 .1. E. BE'vlNs 2,612,753

CONSTANT SPEED PUMP ANO MOTOR HYDRAULIC TRANSMISSION Filed Nov. '7, 19475 Sheets-,Sheet 3 ATTORNEY Oct. 7, 1952 .1. E. BEvlNs 2,612,753

CONSTANT SPEED PUMP AND MOTQR HYDRAULIC TRANSMISSION Filed NOV. 7, 19475 Sheets-Sheet 4 'IIIA INVENTOR ATTORN EY J. E. BEVINS Oct. 7, 195

CONSTANT SPEED PUMP AND MOTOR HYDRAULIC TRANSMISSION 5 Sheets-Sheet 5Filed Nov. 7. 1947 INVENTOR jfl/7755 E @E V//v5 ATTORNEY Patented Det.7, 1952 CFFICE CONSTANT SPEED PUMP AND MOTOR HYDRAULKC TRANSMISSION`llames Emil Bovins, Ramsey, N. J., vassigner to Bendix AviationCorporation, Teterboro, N. J., a corporation of Delaware ApplicationNovember 7, 1947, Serial No. 784,708

This invention relates to constant speed transmissions, and particularlyto a transmission of the hydraulic pump and motor type driven atvariable speed, as by an aircraft engine.

Former devices of such character have been unduly heavy, have not heldup in operation, are subject to excessive wear and have otherdisadvantages not adapting them particularly well to aircraft service.

An object of the present invention is to provide a device of theabove-indicated character which is lighter in weight, holds up inoperation over longer periods of time, is subject to less wear and hasother advantages over prior devices for comparable duty, rendering it aneffective aircraft accessory.

Another object is to provide a constant speed drive, comprisinghydraulic motor, pump and control units, which will hold a substantiallyconstant output motor speed of a predetermined number of revolutions perminute, such as 6000i300 R.. P. M., over a given range of pump inputspeeds, such as 2100 to 9000 R. P. M., at a continuous horsepowerrating, such as fty, at input speeds over a given range, as between 3600and 9000 R. P. M.

Another object is to provide a drive as aforesaid having a speedcharacteristic such that two or more thereof are adapted for paralleloperation to drive alternators, and to have the power divided withinreasonable limits by a built-in linear droop mechanism providing a speedregulation within denite percentage limits, such as eight per cent droopfrom no load to one hundred and fty per cent load in the alternator.

Another object is to provide a transmission of the above-indicatedcharacter which is simple and durable in construction, economical tomanufacture, and effective in its operation.

The above and other objects and features of the invention will appearmore fully hereinafter from a consideration of the following descriptiontaken in connection with the accompanying drawings wherein oneembodiment of the invention is illustrated by way of example.

In the drawings:

Figure 1 is a schematic diagram of a trans` mission embodying theinvention, showing, in each of its pump and motor units, only `one ofseveral pistons of the actual structure, there being actually fifteenpistons in each unit;

Figure 2 is a side view, generally in section, of a portion of theactual motor unit;

Figure 3 is a detail view of a tirnin'g valve sembly indicated in Figurel, taken at right 6 Claims. (Cl. 60-53) 2 angles thereto, there actuallybeing two of such assemblies in the device;

Figure 4 is a sectional view of a detail of the actual structurecorresponding to a View taken substantially along the line 4-4 of Figurel;

Figure 5 is a diagram showing, at the left, a fragment of La motorpiston and cam; at the center, a portion of the timing valve assembly ofFigure 3, and, at the right, a valve cam andanother portion of thetiming valve of Figure 3, all as positioned in relation to each other ata certain phase or step of the motor operation, when duid flow to orfrom the motor piston is completely shut off;

Figure 6 shows the parts of Figure 5 as related at a next subsequentstep of operation, when the motor piston is'fully subjected to thepressure fluid;

Figure 7 shows the parts of Figure 5 as related at a third successivestep of operation, in

which the pressure and exhaust uids are again completely shut oir fromthemotor piston; and

Figure 8 shows the parts of Figure 5 as related at a fourth successivestep of operation, in which the valve is fully open for discharge offluid from the motor piston to a sump.

Referring to Figure l, an aircraft hydraulic transmission unit Il)comprises a housing I2 having a sump I4, an engine driven shaft I5 of apump i8, and a shaft 20 of a uid motor 22 adapted to drive a generator.

Referring to Figure 2, since Figure 1 illustrates only one piston andassociated parts in the pump i8, and only one piston and associatedparts in the -fluid motor 22, the subsequent description should be readwith the actual structure of the motor 22 of Figure 2 in mind, thelatter figure also constituting, in effect, a showing of the pump lil,since the only substantial dilference between corresponding portions ofthe motor and the pump resides in the areas of the pump pistons whichare larger than the areas of the motor pistons.

Eccentric cams 24 are fixed relative to the motor shaft 2li, Whereaseccentric cams 2t, only one of which is shown in Figure 1, are movablymounted on the pump shaft I6, and are adapted to vary the pump outputwith the pump and motor cams 26 and 24, respectively, each havingsegmental surface grooves 28, Figures 5-8, adapted to receive fluidfrom,.and'to discharge iiuid to, the sump I6, respectively. For purposesof clarity, only one cam 26 is shown in Figure 1, it being understoodthat the banks of pistons disposed on either side of pistons 36, shownin 'Figure 1 are each provided with a cam 2E.

Pump and motor blocks 30 and 32, respectively, each embodies an oddnumber of cylinder banks, in this case three, see Figure 2, offset alongits shaft, with the cylinders 3| and 33 of the odd banks of the motorand pump, respectively, symmetrically offset from the cylinders 34 ofthe even bank or banks about its shaft, and having total cylinder areasubstantially equal to the total even bank cylinder area.

A fluid pressure collector 38 is indicated in Figure 1 as in the form ofan annular circular section channel having outlets 39. The cylinders 3|and 34 of the motor 22 have inlets 42 from the collector 38, and thecylinders 33 of the pump |8 have outlets 46 to the collector 38, whichoutlets 46 are provided with ten poppet valves 48 controlling fluid flowfrom the pump to the collector 38.

Pump cam eccentricity varying means 50, associated with the pumpshaftI6, and to be further set forth, is adapted to be actuatedbymeansincluding a servo piston 54 aligned with the shafts I6 and 20.

The cylinders 3|, 33 and 34 enclose pistons 35,

36 and 31, respectively, each of the throughopens housing I2, as byvbolts 63, and having `radial cylinders 64 communicating with thecollector outlets 39 and the motor inlets 42, as seen in Figures 1 and5-8. Plungers 66 having lands 61 in the cylinders 64 arel biased, bysprings 68, against a cam 10 eccentrically mounted on the shaft 20. Thesprings 68 are backed by washers 12 and lock rings 14, Figure 3.

Although only one radial valve means 60 is indicated inthe diagram ofFigure 1, there are actually two of such means. Also, the plungers 66,instead of being maintained on the cam 10 by the springs 68 may bemaintained as are the cam shoes 56 at Figure 2 wherein the shoes aremaintained by rings 15, also indicated in Figure 1. The plungers 66 mayalso be maintained by fluid pressure.

Pump fluid operated control means 16, Figure 1, controlled bycentrifugal means 18 responsive to the rate of rotation of the motorshaft `2|), is adapted to regulate the servo piston 54 in maintainingthe pump output and the rate of rotation of the shaft 20 atsubstantially constant values between zero load and a given overload, asabove mentioned, irrespective of variations in the speed of the pumpshaft I6. The means 16 includes means 80 responsive to loads on themotor shaft 20 providing for a change in the motor shaft speed withindefinite percentage limits of the above-mentioned constant values.

The pump cam eccentricity varying means 50, see also Figure 4, comprisesa square-section portion 82 of the pump shaft I6, having sliding fit inrectangular holes 84 of the pump cams 26. A rod 86, actuated by theservo piston 54 is axially slidable in the shaft portion 82 and carriesa pin 92 slidably fitting a cam slot 94 in each of the cams 26.

Movement of the servo piston 54, right or left, as viewed in Figure 1,acts through the rod 86, the pins 92 and the axially sloping camsurfaces '4 defining the slots 94 to vary the radial distance betweencam surfaces of the cams 26 and the axis of the shaft I6, thus varyingthe lengths of the strokes of the pump pistons.

A pair of ball bearings 96, Figure 1, are mounted between the rod 86,which rotates with the pump shaft I6, and the non-rotative servo piston54, which is sealed by ring seals 98 and |00.

The pump shaft I6 is journaled, at opposite sides of its cams 26, inball bearings |02, and provided near its outer end with a bellows seal|04. The motor shaft 20 is journaled, at opposite sides -of its cams 24,in ball bearings |06, and

provided near its outer end with a bellows seal |108.

'The vcentrifugal means 18, Figure 1, comprises ashaft I|0 journaled inbearings |I2 having a gear |'|4, Figure 1, adapted to engage and berotated by a gear |I6, Figure 2, on the moto-l` shaft 20. A governordevice I|8 comprises a support |20 fixed to the shaft |I0, to whichsupport .are pivotally mounted, by pins |22, bell `crank weight levers I24 held, when stationary, against astop |26, by a spring or springs |28.

When the shaft vI I0 rotates, portions |30 of the bell cranks |24, raisea rod |32 to cause a beam |34 of the means 16 to pivot about a pin |36which is eccentrically adjustable about an axis |38 in a slot |44. Tocompensate for such adjustment, a screw |46 may be adjusted relative toa needle valve pin |48 which it depresses against the action of a spring|50 associated with a servo cylinder |54, relative to an orifice |56 ina servo pilot Aplunger |58. The orifice |56 leads into a chamber |51containing a port |59 which communicates with the exterior of the servocylinder |54. The pilot plunger |58 is slidable in a droop sleeve |60over a spring |62 in the sleeve, and has ,lands |64 and |66, at oppositesides of a side duct |68 in the sleeve 60, and controls ducts |10 and|12, respectively, also in the sleeve |66. The duct |68 registers with aconduit |14, and theducts |10 and |12 communicate with conduits |16 and|18, respectively, leading to the left and right hand sides,respectively of the servo piston 54, as indicated in Figure 1. Droopsleeve |60 is also provided with a drain port |19 to permit exhaustingof servomotor 54 when it moves to the right as shown in Figure 1.

The conduit |14 communicates with a reducing valve |80, comprising acasing |82, a sleeve |84, a spring |86, and a plunger |88, the casing|82 having an inlet |90 from the collector 38.

A droop valve y'|92 comprises a casing |94 connected to the inlet |90,and containing a plunger |96 biased upwardly, as shown, by a spring- |98extending between the bottom of the casing |94 and a disc I 99. Twoballs 200 operate as a non binding piston under the high pressuresinvolved.

The plunger |96 and the droop sleeve |60 are connected by alink 202having a slot 204 in which a pivot pin 206 is free to ride. The pin 206is attached to a member 208 which in turn slidably mounted on thesupport 2|0 so that by sliding the member 208 along the support 2|0, thepin 206 may be adjusted in any desired position in slot 204.

In operation, on the intake stroke, hydraulic oil is drawn through theapertures 58 of the pump piston shoes 56 from the sump I 4, the latterbeing defined by the housing |2, which is filled with oil and held atinlet pressure of approximately ten to fifteen pounds per square inch.

On the compression stroke of each piston 36,

the poppet valves 48 are opened, when the pressure build up is greaterthan the vpressure in the collector 38, allowing the oil to flow intocollector. Thus, there are fteen pump pistons 36 so displaced as toeffect a relatively even flow of oil through the ten poppet valves d8 tov the collectori.

Since the speed of the motor 22 must bel substantially constant, theflow from they pump I8 must be correspondingly constant over a pumpinput speed range, in this instance, of fromg2000 to 9000 R. P. M.Substantially constant flow from the pump i8 is obtained by varying theI8 is accomplished by means of the control means 76 and the master servo5d operating in conjunc-Y tion with the variable stroke pump cams 25.

An increase in the speed of the motor shaft acts through the gear H5,Figure 2; the gear i i4, Figure 1, the shaft I i0, the portions |30, therod |32, the beam |36, and the screw |45 to cause a downward motion ofthe needle valve pin |68 which, in turn, starts to close the orificei.Since the conduit |74 communicates with the casing |32 which in turn hasan inlet |99 frorn'the collector 3S, pressure is built up in the servopilot cylinder |54 which moves the servo pilot |58v downwardly, allowingQil under pressure to vfiow into the conduit |18 which communicates withthe cylinder of the master servo piston 5i,`thus moving the piston 5d tothe left and decreasing the stroke of the pump pistons 35 by moving thepins 32 such as to move the high points of the pump cams 26 closer tothe axis of the pump shaft I6.

A decrease in the speed of the motor shaft 2li conversely allows theservo pilot 5t to move upwardly by spring 62, allowing oil under.pressure to flow into the conduit |16, thus moving the mas'- ter servopiston 54 to the right and increasing the stroke of the pump pistons.

To obtain the 8% droop, desired in this inf,

stance, over a load range of 0 to 150%, the niember 208, Fig-ure l, isadjusted along the support 210 to adjust the position of the pin 255 sothat', at any point between 0 and 150% load, the speed of the motor 22will correspond to a predetermined value determined from a speed-loadcurve incorporating the 8% droop. The relative positions of the droopsleeve |50 and the servo pilot G53 are set by the adjusting slidingpivot 205 `to give the required droop characteristics.

In the operation of the motor 22, hydraulic oil under pressure in thecollector 38 is ported to the motor pistons 35 and 37 in proper sequenceby the valve plungers t6 operated by the cam it on the motor shaft 20.

In Figure 5, the piston 35 is atthe ton of its Figure 6. This pressureon the piston exerts'al force tending to rotate the motor-shaftlinithecounterclockwise direction indicated by an arrow,

as shown.

In'Figure 6, the pistonf35 is shown as lposi-'- tioned after'the shaft20 has rotated 90 from its position of Figure 5. Itis half way on theIdown stroke, Vwhereas'theA timing valve plunger 6G has reached itslowermost position. At this stage, the inlet port 42 to the cylinder ofthe piston 35 is wide'open, and the piston is undery the full pumpoutlet pressure of the oil from the outlet 39.'

`- The port 2te the piston 35 will be gradually closed-during the 'nextfollowing 90 rotation of the shaft 2li until, as in Figure "I, itis'completely closed again as' it is in Figure 5, the only differencebeing that the piston 35 is now at the bottom of the stroke andthetiming valve 66 again at half stroke. v During thenext subsequent 90rotation of the shaft 20, theV port 42 will be gradually opened, but,this time, to the inlet side allowing, oil to be discharged through'theport e2 by'way of the plunger 'B6 to the sump. Oil is also dischargedthrough the piston shoe by way of the groove 28 while the piston `35 ison'its up stroke.

At the position of Figure 8,`the piston is `half way'on yits up strokeand the timing valve 56 is at the `top of'its stroke, at which time thevalve port 42 is wide open to the inlet side of the drive. During thenext subsequent rotation, the valve 'port t2 is gradually closed,allowing oil to ow from the piston vto the inlet'side until the valveport 42 is completely closed, as in Figure 5.

Gil is also allowed to flow through the piston shoe by Way ofthe groove28 to the inlet side until the piston shoe is over the solid section ofthe camfasindicated in Figure 5.

Although only one embodiment of the invention has been illustrated anddescribed, various changes in` the form and relative arrangements of theparts may be made to suit requirements.

What is claimed is: f

1,'InV an aircraft hydraulic transmission, the combination of a sump,'an engine driven `pump shaft, a motorshaftto drive a generator,eccentric cams xed to the motor shaft, eccentric cams movable on thepump shaft to vary the pump output-the pumpand motor cams havingsegmental'cam surfacegrooves to receive fluidfrom and to discharge fluidto the sump,` respectively, Dump and motor blockseach embodying an oddnumber of cylinder banks oiset along its shaft with the cylinders of theodd banks symmetrically onset from the cylinders of the even bank orbanks about its shaftv and having total cylinder areasubstantiallyequal' to the total even bank cylinder area, a pump outputcollector, the motor cylinders having inlets from the collector and thepump cylinders having outlets to the collector, poppet valve meanscontrolling the delivery of the pump output to the collector, pump cameccentricity varying means associated with' the pump shaft, meansincluding a servo piston aligned with the shafts for actuating saideccen tricity varying means, a through opening tubular pistonv inv eachcylinder including a. pivoted cam shoel havinga carn engaging surfaceaperture between its cylinder andcam, radial valve means to distribute'pump y' output from the collector to the motor cylinders, eccentricmeans on the motor shaft fcroperating said radial valve means,centrifugal means responsive to motor shaft speed;

pump pressure responsive means, and pump fluid operated valve meanscontrolled by joint operation of said centrifugal and pump pressureresponsive means to regulate the servo' piston in maintaining said pumpoutputI and said motor shaft speed `at substantially constant valuesbetween zero load and given overload irrespective of variations in thespeed of; the pump s haftand providing for a change-in the motor shaftspeed withinv definite percentage limits of said constant values.

2. In a. hydraulic transmission, the combination of a pump shaft, amotor shaft, eccentric cams fixed to the motor shaft, a sump, movableeccentric cams on lthe vpump shaft to vary the pump output, the pump-andmotor -camslhaving segmental cam surface-grooves to receive fluid fromand to discharge f'luid to the sump, respectively, pump and motor blockseach embodying an odd number of cylinder banks offset along its shaftwith the cylinders of the odd banks symmetrically offset from thecylinder or cylinders of the even bank or banks about its shaft andhaving total cylinder area. substantially equal to the even bank totalcylinder area,a pump output collector, the motor cylinders having inletsfrom the collector and the pump cylinders having outlets to thecollector, valve means controlling delivery of the pump output -to thecollector, pump cam eccentricity varying means, means including a servopiston to actuate said eccentricity varying means, a through openingtubular piston in each cylinder including a pivoted cam shoe having acam engaging surface aperture between its cylinder and cams, radialvalve means to distribute pump output from the collector to the motorcylinders, eccentric means on the motor shaft for operating said radialvalve means, centrifugal means responsive to motor shaft speed, pumppressure responsive means and pump fiuid operated valve means controlledby the joint operation of said centrifugal and pump pressure responsivemeans to regulate the servo piston in maintaining said pump output andsaid motor shaft speed at substantially constant values between zeroload and given overload irrespective of variations in the speed of thepump shaft and providing for a change in the motor shaft speed withindefinite percentage limits of said constant values.

3. In hydraulic transmission means, the comhaving segmental cam surfacegrooves to receive fluid from and to discharge fluid to the sump,respectively, pump and motor blocks each embodying an odd number ofcylinder banks offset along its shaft with the cylinders of the oddbanks symmetrically-offset from the cylinder or cylinders of the evenbank or banks about its shaft and having total cylinder areasubstantially equal to the even bank total cylinder area, a pumpoutputcollector, the motor cylinders having inlets from said collector and thepump cylinders having outlets to the collector, valve means controllingdelivery of pump output from the pump to the collector, pump cameccentricity varying means, servo means to actuate said eccentricityvarying means, a through opening tubular piston in each cylinderincluding a pivoted cani shoe having a cam engaging surface aperturebetween its cylinder and cam, a valve device to distribute the pumpoutput from the collector to the motor cylinders, means operating saidvalve device from the motor shaft, centrifugal means responsive to motorshaft speed, pump pressure responsive means, and pump fluid operatedvalve means controlled by the joint operation of said centrifugal andpump pressure responsive means to regulate said servo means inmaintaining said pump output and said motor shaft speed at substantiallyconstant values between zero load and given overload irrespective ofvariations in the speed of the pump-shaft.

4. In hydraulicl transmission mean-s, the combinatlon of a sump, a fluidoperated motor including outlet means to the sump and having a shaft, acollector, a pump including a shaft and connected to pump fluid from thesump to the collector, means including valve means for controlling thedelivery of pump output from the pump to the collector. means to varythe output of the pump, said vary means comprising a plurality ofeccentric cams on the pump shaft rotative herewith and radially movablerelative thereto, the pump shaft being hollow and having sloping slotsto increase and decrease eccentricity of the cams, a rod axially movablein the pump shaft, and pins projecting laterally from the rod anddisposed one extending through each of said sloping slots, a pistonconcentric with said pump shaft to move the rod axially, valve meansdistributing the pump output from the collector to the motor foractuating the motor, centrifugal means responsive to motor shaft speed,pump pressure responsive means, and valve means controlled by the jointoperation of said centrifugal and pump pressure responsive means toactuate said piston and thereby said pump output varying means inmaintaining said pump output and said motor shaft speed at substantiallyconstant values between zero load and given overload irrespective ofvariations in the speed of the pump shaft.

5. In hydraulic transmission means, the combination of a sump, a fluidoperated motor including outletvmeans to the sump and having a shaft, acollector, a pump including a shaft and connected to pump fiuid from thesump to the collector, means including valve means for controlling thedelivery of pump output from the pump to the collector, means to varythe pump output, said varying means comprising a plurality of eccentriccams on the pump shaft rotative therewith and radially movable relativethereto, means including a rod axially movable in the pump shaft to movesaid cams radially, and piston means to move the rod axially, valvemeans distributing the pump output from the collector to the motor foractuating the motor, centrifugal means responsive to motor shaft speed,pump pressure responsive means, and valve means controlled by saidcentrifugal and pump pressure responsive means to actuate said pistonmeans and thereby the pump output varying means in maintaining said pumpoutput and said motor shaft speed at substantially constant valuesbetween zero load and given overload irrespective of variations in thespeed of the pump shaft.

-6. In hydraulic transmission means, the combination of a sump, a fluidoperated motor including outlet means to the sump and having a shaft, acollector, a pump including a shaft and connected to pump fluid from thesump to the co1- lector, means including valve means for controlling thedelivery of the pump output from the pump to the collector, meansincluding piston means to vary the out'put of the pump, radial valvemeans controlling the delivery of pump output from the collector to saidmotor for actuating the motor, radial valve actuating means includingeccentric means carried by the motor shaft, centrifugal means responsiveto motor shaft speed, pump pressure responsive means, and valve meanscontrolled by joint operation of said cen- 9 trifugal and pump pressureresponsive means to actuate said piston means and thereby the outputvarying means in maintaining said output and said motor shaft speed atsubstantially constant values between zero load and given overloadirrespective of variations in the speed of the pump shaft.

JAMES EMIL BEVINS.

REFERENCES CITED The following references are lof record in the file ofthis patent:

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